1. Field of the Invention
The present invention relates to a C-axis driving device of a computer numerical controlled (or briefly called CNC) lathing and milling machine. Particularly, by easily switching the spindle motor and the servo motor as started (there are torque output) or released (no torque output), it can achieve both the lathing work and the milling work on this CNC machine.
2. Description of the Prior Art
One of the traditional C-axis driving device of a computer numerical controlled (or briefly called CNC) lathing and milling machines can be seen in FIG. 7. With regard to the C-axis driving device, a conventional servo motor 71 is disposed above a spindle of a housing. Also, a double-lead worm 72 driven by the conventional servo motor 71 is disposed on this housing. All the description about other related elements is omitted here. The first disadvantage is that its structure is too complicated. In addition, because its switch action is based on direct contact with a gear (or worm), a back-lash problem occurs. Therefore, due to such back-lash, when a user control this CNC machine to drive the C-axis system, it cannot move to a desired position nor mill a profile of a work piece very precisely. So, such conventional device is not commonly-used now.
In addition, some company develops another kind of servo motor that can be used as a spindle motor too. But, such servo motor cannot meet the requirements of high speed and large torque output (for lathing work) and precise positioning control (for milling work).
Furthermore, there is a combined spindle motor (not shown, such as the model No. αP18i of FANUC company). It contains the characteristics of high speed and large torque output (for lathing work) as well as the precise positioning control (for milling work). However, such combined spindle motor is extremely expensive and it only can be controlled by the CNC controller made by the FANUC company. Thus, the manufactures in this industry cannot use other lower-priced CNC controller (not made by FANUC company) to control this kind of combined spindle motor. Therefore, there is a widely need for this industry to develop a new C-axis driving device to solve he above-mentioned problems.